The present invention relates to the field of variable displacement bent axis hydraulic units. More particularly, this invention relates to a swingable yoke for a bent axis unit.
Bent axis hydraulic units have been known for many years. However, one of the most persistent challenges facing bent axis designers is the provision of a cost-effective and reliable yoke for carrying the cylinder block kit and varying the displacement of the bent axis unit.
One known transmission utilizes a two-piece yoke design. This design combines an upper trunnion piece with a separate bolt-on endcap. This design relies on dowel pins to locate the endcap to the upper body. Seals are required for high-pressure transition passages and joints between the two parts. Furthermore, several bolts are required to hold the two parts together. The endcap must usually be made utilizing a slow and costly lapping process.
Therefore, a primary objective of the present invention is the provision of a one-piece yoke for a swinging bent axis hydraulic unit.
Another objective of this invention is the provision of a yoke that has a surface for supporting a cylinder block kit in the bottom of its bucket portion.
Another objective of the present invention is the provision of a yoke that has a pair of integrally formed fluid passages connecting the supporting surface to the control trunnion without leaving the wall of the yoke.
Another objective of the present invention is the provision of a yoke which has all of the system pressure and gauge ports located on a single trunnion.
Another objective of the present invention is the provision of an integral shoulder on the yoke for stopping its pivotal movement.
Another objective of the present invention is the provision of a yoke which is economical to manufacture, minimizes the number of parts required, and is reliable in use.
These and other objectives will be apparent from the drawings, as well as from the description and claims which follow.